fix(replay): Fix visual artifacts for the Canvas strategy on some devices#4861
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fix(replay): Fix visual artifacts for the Canvas strategy on some devices#4861
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romtsn
requested review from
adinauer,
lcian,
markushi and
stefanosiano
as code owners
![sentry[bot]](https://avatars.githubusercontent.com/in/12637?s=60&v=4){kind=small}
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104
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110
| { result -> | ||
| if (result == PixelCopy.SUCCESS) { | ||
| lastCaptureSuccessful.set(true) | ||
| val bitmap = screenshot | ||
| if (bitmap != null && !bitmap.isRecycled) { | ||
| screenshotRecorderCallback?.onScreenshotRecorded(bitmap) | ||
| } |
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Bug: Unsynchronized access to screenshot Bitmap by multiple threads while another thread recycles it.
Severity: CRITICAL | Confidence: 1.00
🔍 Detailed Analysis
The screenshot Bitmap is accessed without synchronization by emitLastScreenshot() on the main thread and by the PixelCopy callback on a background handler thread. Concurrently, the close() method, executing on a thread pool, recycles the same screenshot Bitmap. This creates a data race where the Bitmap can be accessed after it has been recycled, which can lead to native crashes according to repository guidelines.
💡 Suggested Fix
Protect all accesses to the screenshot Bitmap with synchronized(bitmap) blocks to prevent concurrent access during recycling or other operations.
🤖 Prompt for AI Agent
Review the code at the location below. A potential bug has been identified by an AI
agent.
Verify if this is a real issue. If it is, propose a fix; if not, explain why it's not
valid.
Location:
sentry-android-replay/src/main/java/io/sentry/android/replay/screenshot/CanvasStrategy.kt#L104-L110
Potential issue: The `screenshot` Bitmap is accessed without synchronization by
`emitLastScreenshot()` on the main thread and by the PixelCopy callback on a background
handler thread. Concurrently, the `close()` method, executing on a thread pool, recycles
the same `screenshot` Bitmap. This creates a data race where the Bitmap can be accessed
after it has been recycled, which can lead to native crashes according to repository
guidelines.
Did we get this right? 👍 / 👎 to inform future reviews.
sentry-android-replay/src/main/java/io/sentry/android/replay/screenshot/CanvasStrategy.kt
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![cursor[bot]](https://avatars.githubusercontent.com/in/1210556?s=60&v=4){kind=small}
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Contributor
Performance metrics 🚀
|
| Revision | Plain | With Sentry | Diff |
|---|---|---|---|
| 2124a46 | 319.19 ms | 415.04 ms | 95.85 ms |
| b3d8889 | 420.46 ms | 453.71 ms | 33.26 ms |
| d217708 | 409.83 ms | 474.72 ms | 64.89 ms |
| 3d205d0 | 352.15 ms | 432.53 ms | 80.38 ms |
| fcec2f2 | 357.47 ms | 447.32 ms | 89.85 ms |
| 889ecea | 367.58 ms | 437.52 ms | 69.94 ms |
| 1df7eb6 | 397.04 ms | 429.64 ms | 32.60 ms |
| ce0a49e | 532.00 ms | 609.96 ms | 77.96 ms |
| ee747ae | 357.79 ms | 421.84 ms | 64.05 ms |
| b750b96 | 408.98 ms | 480.32 ms | 71.34 ms |
App size
| Revision | Plain | With Sentry | Diff |
|---|---|---|---|
| 2124a46 | 1.58 MiB | 2.12 MiB | 551.51 KiB |
| b3d8889 | 1.58 MiB | 2.10 MiB | 535.07 KiB |
| d217708 | 1.58 MiB | 2.10 MiB | 532.97 KiB |
| 3d205d0 | 1.58 MiB | 2.10 MiB | 532.97 KiB |
| fcec2f2 | 1.58 MiB | 2.12 MiB | 551.50 KiB |
| 889ecea | 1.58 MiB | 2.11 MiB | 539.75 KiB |
| 1df7eb6 | 1.58 MiB | 2.10 MiB | 532.97 KiB |
| ce0a49e | 1.58 MiB | 2.10 MiB | 532.94 KiB |
| ee747ae | 1.58 MiB | 2.10 MiB | 530.95 KiB |
| b750b96 | 1.58 MiB | 2.10 MiB | 533.19 KiB |
Previous results on branch: rz/fix/session-replay-canvas-artifacts
Startup times
| Revision | Plain | With Sentry | Diff |
|---|---|---|---|
| a47b2db | 372.31 ms | 463.36 ms | 91.05 ms |
| 51bd5cc | 360.74 ms | 464.40 ms | 103.65 ms |
| bd9a863 | 300.79 ms | 361.92 ms | 61.13 ms |
| 7e17e61 | 314.77 ms | 337.06 ms | 22.29 ms |
App size
| Revision | Plain | With Sentry | Diff |
|---|---|---|---|
| a47b2db | 1.58 MiB | 2.12 MiB | 551.78 KiB |
| 51bd5cc | 1.58 MiB | 2.12 MiB | 551.66 KiB |
| bd9a863 | 1.58 MiB | 2.12 MiB | 551.65 KiB |
| 7e17e61 | 1.58 MiB | 2.12 MiB | 551.75 KiB |
sentry-android-replay/src/main/java/io/sentry/android/replay/screenshot/CanvasStrategy.kt
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sentry-android-replay/src/main/java/io/sentry/android/replay/screenshot/CanvasStrategy.kt
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📜 Description
Example replay: https://sentry-sdks.sentry.io/explore/replays/09456bd8f08c43eb862a23759d1dc640
💡 Motivation and Context
Closes #4857
💚 How did you test it?
📝 Checklist
sendDefaultPIIis enabled.🔮 Next steps